The computerized tomography (CT) apparatus generally comprises a scan device and a display device. The scan device scans an object to be diagnosed by emitting X-rays to the object to be diagnosed and receiving X-rays penetrating the object to be diagnosed, so as to obtain a scanning image that reflects the degree of absorption of X-rays by each site of the object to be diagnosed. The scan device further provides the obtained scanning image to the display device which displays the scanning image. Hence, an operator (e.g., a doctor) can observe the scanning image displayed by the display device, and determine whether there exists a lesion site in the scanning image.
The scanning image comprises a plurality of pixels, each pixel having gray scale corresponding to CT value, wherein the CT value represents the degree of absorption of X-rays by the site of the object to be diagnosed to which the pixel corresponds. Typically, the higher CT value represents a higher degree of absorption of X-rays, and the lower CT value represents a lower degree of absorption of X-rays. For example, the CT value of pixel corresponding to bone tissue is set to be +1000 Hu, the CT value of pixel corresponding to water 0 Hu, the CT value of pixel corresponding to air −1000 Hu, etc.
The CT value of pixel can be converted to a gray scale of pixel by setting an appropriate window width (WW) and window level (WL). The window width is a CT value range of pixels that will be displayed by different gray scales, i.e., pixels within the CT value range are displayed by different gray scales, the pixel with the CT value higher than this range is displayed as the maximum gray scale value, and the pixel with the CT value lower than this range is displayed as the minimum gray scale value. The window level is the central position of the window. For example, when the window width is 100 Hu and the window level is 0 Hu, the CT value range of pixels that will be displayed by different gray scales −50 Hu˜+50 Hu.
In order to determine whether there exists a lesion site in the scanning image, the operator (e.g., doctor) may need to frequently and manually input new window width and/or window level to change the gray scale of pixel of the scanning image, so as to repetitively compare the differences between the scanning image that is initially displayed on the display device according to the initial window width and window level and the new scanning image that is displayed on the display device according to the new window width and/or window level, until it is determined whether there exists a lesion site in the scanning image.
In addition, when determining whether there exists a lesion site in the scanning image, the operator (e.g., doctor) may need to locally change the gray scale of pixel of the scanning image, e.g., changing the gray scale of pixel in the region of interest (ROI), so as to compare the region having the gray scale changed with other regions adjacent to it. However, since the scanning image wholly changes the gray scale of pixel according to the new window width and/or window level input by the operator (e.g., doctor), such need cannot be satisfied.
Therefore, a display device, which can simplify operations and enhance diagnosis reliability upon diagnosis, is needed.